Many computerized information retrieval systems have been developed, including both bibliographic and full-text systems. However, computerized information systems are not yet widely used or accepted by health care practitioners. Only limited evaluation of computerized medical information systems exist. The evaluation that have been done have generally concerned the technical utility of prototype systems or have utilized physicians in university medical centers. In the area of drug information, widely recognized as an area of need by physicians, none of the large commercially available computerized medical information systems have been thoroughly evaluated. This is especially needed for health care personnel in office-based practices. Therefore, the specific aims of this study are: 1) to evaluate and compare the utility of the MEDIS TM and BRS/Saunders Colleague computer information systems as they relate to the provision of drug information to clinical pharmacists, private practice internal medicine, and private practice family practice physicians; and 2) to describe the attitudes of the users with regard to computer access, amount of time it takes to find requested or desired information, work compatibility, search strategy of information, and the use of computers in general. This study will explore how the systems are accepted and utilized by health care practitioners, and will examine characteristics of the system that affect their utilization. This study will also help identify what the day-to-day information needs of health care practitioners actually are. If the computer systems are not found to be as beneficial as they could be, then specific improvements or enhancements can be explored. If the systems are utilized and perceived to be beneficial, then further studies can probe the effects of the systems on patient outcomes. The first period of the study will describe the sources of drug information used by the subject (pre-computer). One of the computer systems will then be installed in each setting, and the subject trained in its use. Preliminary use and attitude data will be collected. During the next 10 month period, frequent multiple measures of computer utility and attitude will be collected. The process will then be repeated in each subject setting using the second computer system. Both use and attitude data will be analyzed within and between subjects and settings. The entire study and analysis portions will extend over a three year time period.